Source : Webster's Revised Unabridged Dictionary (1913)

Cock-a-hoop \Cock`-a-hoop"\, a.
   Boastful; defiant; exulting. Also used adverbially.

Source : WordNet®

cock-a-hoop
     adj : exhibiting self-importance; "big talk" [syn: {boastful}, {braggart(a)},
            {bragging(a)}, {braggy}, {big}, {crowing}, {self-aggrandizing},
            {self-aggrandising}]